William Halpern asserts that 'human nature' needs 'to be considered alongside the purely political and economic issues 'to get closer to the truth about the nature of war' (Letters, March SR).
Like other arguments from human nature, this presupposes that some trait, say the ability to learn a human language, or violence, is genetically hardwired into the human organism--that it is part of what it means to be human to manifest the trait. This is a very strong claim. A single counterexample--a society whose institutions do not express or promote greed or violence--means that we have to scrap or modify the assumption and reconstruct any arguments that rest on it. 'The exception proves (ie tests) the rule.'